Image forming apparatus, pattern position determining method, and image forming system

Abstract

An image forming apparatus is disclosed which reads a test pattern, including a reading unit, a relative movement unit, a second detected data obtaining unit which obtains one or more second detected data sets of a reflected light which is received from a scanning position of a light by a light receiving unit while the reading unit moves relatively with respect to the recording medium before the test pattern is formed, a first detected data obtaining unit which obtains one or more first detected data sets of the reflected light which is received by the light receiving unit when the light moves over the test pattern at generally the same scanning position as the scanning position while the reading unit moves relatively with respect to the recording medium after the test pattern is formed, and a signal correction unit.

Description

TECHNICAL FIELD[0001]The present invention generally relates to liquid-ejecting image forming apparatuses and more specifically relates to an image forming apparatus which can correct an offset of an impacting position of liquid droplets.BACKGROUND ART[0002]Image forming apparatuses (below called liquid ejecting image forming apparatuses) are known which eject liquid droplets onto sheet material such as a sheet of paper to form an image. The liquid ejecting image forming apparatuses may generally be divided into a serial-type image forming apparatus and a line-head type image forming apparatus. In the serial-type image forming apparatus, a recording head moves in both main scanning directions perpendicular to a direction of sheet conveying while the sheet conveying is repeated to form an image over the sheet of paper. In the line head-type image forming apparatus with nozzles being aligned in a length which is almost the same length as a maximum width of the sheet of paper, when a t...

AI Technical Summary

Benefits of technology

The present invention provides an image forming apparatus that can adjust the timing of liquid droplets to accurately position a test pattern, even if the sheet material used has certain characteristics. The apparatus includes a reading unit that moves relative to the recording medium and detects reflected light from the medium, a first detected data obtaining unit that detects the light when the reading unit moves over the test pattern, and a signal correction unit that calculates a ratio of the first detected data to the second detected data to align the local maximum value. This allows for precise positioning of the test pattern and accurate adjustment of the liquid droplets ejection timing.

Problems solved by technology

Moreover, it is known that, in the line head-type image forming apparatus, parallel lines are likely to appear in the sheet-conveying direction when there is a nozzle whose position of impacting is constantly offset due to a mounting error, a finishing accuracy of the nozzle, etc.

However, the correcting of the liquid droplet ejection timing as disclosed in Patent document 1 has the following problems.

As is well known, light is absorbed well by a black object, so that it is difficult for the spotlight to be reflected when the test pattern is scanned if a sheet material is white and the test pattern is black.

However, there is a problem that, when a sheet material is a material with a low reflectance (or a high transmittance), such as a tracing paper, it is difficult for a detected voltage of the light receiving element to be stable, so that the edge position of the test pattern may not be specified accurately.

In other words, for the sheet material with the low reflectance, the amplitude of the voltage value becomes small, or an amplification of sensor sensitivity or a variation in transmittance of the sheet material leads to a large variation in the voltage value, leading to instability.

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